Add EEPROM EUI-48 device identity across firmware and API.

Read the factory 24AA025E48 serial after ADAU I2C boot, derive SoftAP SSID, BT name, STA hostname, and expose serialNumber on GET /api/health with graceful fallbacks.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/drivers/adau1701/include/adau1701/Adau1701Driver.hpp

@@ -112,6 +112,19 @@ public:
      */
     [[nodiscard]] bool isBooted() const noexcept;
 
+    /**
+     * @brief    i2cBusHandle — borrow the shared I2C master bus after boot.
+     *
+     * @dname    i2cBusHandle
+     * @return   Opaque bus handle for the 24AA025E48 on the same bus, or null
+     *           before boot().
+     * @pubstate reads i2cBus_.
+     *
+     * @author   Michele Bigi
+     * @date     2026-07-07
+     */
+    [[nodiscard]] void* i2cBusHandle() const noexcept;
+
     /**
      * @brief    applyProfile — safeload mixer, EQ, and master from snapshot.
      *

Software/components/drivers/adau1701/src/Adau1701Driver.cpp

@@ -122,6 +122,11 @@ bool Adau1701Driver::isBooted() const noexcept
     return booted_;
 }
 
+void* Adau1701Driver::i2cBusHandle() const noexcept
+{
+    return i2cBus_;
+}
+
 std::expected<void, Adau1701Error> Adau1701Driver::ensureBooted() const
 {
     if (!booted_) {